Blue Light Blues

One by one, all of our warm white lights are being replaced by cold, harsh, bluish-white LEDs. And it is happening fast.

Everywhere. In our streetlights, our workplaces, even our homes. How do you like looking into those blue-white vehicle headlights as compared with the yellow-white ones we have been using since the automobile was invented?

LED lighting is the way of the future, don’t get me wrong, but we should be specifying and installing LED lights with a correlated color temperature (CCT) of 2700K or 3000K—with few exceptions—not the 4000K or higher that is the current standard.

Why is 4000K the current standard? Because blue-white LEDs have a slightly greater luminous efficacy than yellow-white LEDs. Luminous efficacy is the amount of light you get out for the power you put in, often measured in lumens per watt. But should luminous efficiency be the only consideration? What about aesthetics? In addition to luminous efficacy, there are other, more significant ways to reduce power consumption and greenhouse gas emissions:

Use the minimum amount of light needed for the application; no need to overlight

Use efficient light fixtures that direct light only to where it is needed; near-horizontal light creates annoying and visibility-impairing glare and light trespass, and direct uplight into the night sky is a complete waste

Produce the light only when it is needed through simple switches, time controls, and occupancy sensors; or, use lower light levels during times of little or no activity

Even the super-inefficient incandescent light bulb (with a CCT of 2400K, by the way), operating three hours each night uses less energy than the light source with the highest luminous efficacy operating dusk to dawn. Think about it.

In my town, as in most now, the soothing orange 1900K high pressure sodium (HPS) streetlights are being replaced with 4000K LEDs. That’s a big change. It will completely transform our outdoor nighttime environment. Warm-white compact fluorescents are 2700K, and even tungsten halogen bulbs are 3000K. Do we really want or need 4000K+ LEDs?

We are currently witnessing a complete transformation of our illuminated built environment. Not enough questions are being asked nor direction being given by citizens, employees, and municipalities. The lighting industry generally wants to sell as many lights as possible at the highest profit margin. We as lighting consumers need to make sure we have the right kind of light, the right amount of light, and lighting only when and where it is needed.

Higher color-temperature lighting of 3500K or higher is often specified for office lighting during the day to more closely match daylight color temperature, but all to often this type of lighting is also being specified for nighttime use. Lower color temperature lighting of 2700K or 3000K should be used for residential lighting and any other lighting that is primarily being used after sunset, such as streetlighting, parking lot lighting, and security lighting.